Re: ARIANE-5 Failure

["Tronche Ch. le pitre" <tronche@lri.fr>]

John McCabe wrote:
> 
> I have heard that the failure of the Ariane 5 rocket's first launch on
> Tuesday was caused by a software fault in the attitude control system.

French media have presented several successive explanations but always
invoking software failure.
 
> Does anyone know whether Ada was used on that system, and if so, who
> designed and built the software, and which compiler and target were
> used.

Sad to say, but the software is entirely written in Ada, with a few
parts in assembler. It has been described by Jean-Noel Montfort and
Vinh Qui Ribal, from Aerospatiale, in the 2nd Eurospace-Ada in Europe
conf. (1995). Quoted from their paper, the computer boards are Motorola
68020/68881 with 512 kb of RAM, and the Alsys compiler. The software
has been designed using the HOOD methodology.


The launch was broadcast on TV. The greatest time (if I can say that)
was just before the rocket was destroyed. After 40 seconds or so of a
nice launch, it became obvious that it was on a bad trajectory.
Then someone say (the operational director or a journalist, I
don't know) "trajectory and all flying parameters are okay", and just
then BOOOM, someone had noticed that parameters weren't OK at all
and made the rocket exploded...

It would have been very nice if everything had worked well, but
frankly, you take a big risk when you change something on a rocket,
and everything was new on this one, from the engine to the computers.
Thus I'm not surprised. I don't think one has never see number 1 of
any rocket succeeded in the aerospace industry history.


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